The tunnel-structured Na<sub>0.44sub>MnO<sub>2sub> is considered as a promising cathode material for sodium-ion batteries because of its unique three-dimensional crystal structure. Multiangular rod-shaped Na<sub>0.44sub>MnO<sub>2sub> have been first synthesized via a reverse microemulsion method and investigated as high-rate and long-life cathode materials for Na-ion batteries. The microstructure and composition of prepared Na<sub>0.44sub>MnO<sub>2sub> is highly related to the sintering temperature. This structure with suitable size increases the contact area between the material and the electrolyte and guarantees fast sodium-ion diffusion. The rods prepared at 850 °C maintain specific capacity of 72.8 mA h g<sup>–1sup> and capacity retention of 99.6% after 2000 cycles at a high current density of 1000 mA g<sup>–1sup>. The as-designed multiangular Na<sub>0.44sub>MnO<sub>2sub> provides new insight into the development of tunnel-type electrode materials and their application in rechargeable sodium-ion batteries.